RWM Flashcards
What is the purpose of the Rod Worth Minimizer?
Limits amount of reactivity insertion in the event of a rod drop accident.
Design basis is to servce as backup to procedurally conntrol during startup and low power operation to limit control rod worth and reactivity addition rate resulting from control rod drop and thus assure peak fuel enthalpy would be less than 280cal/g
Applies a select block to out of sequence rod when selected to prevent movelment of rod in or out.
When is RWM required?
Required operable up to Rx Power of 10%
How does RWM prevent mis-positioning errors?
It doesn’t. It prevents withdrawing/inserting out-of-sequence control rods. Still can put an in sequence rod to a wrong position.
During a CR Drop Accident, what exists to limit the rate of reactivity addition?
Velocity limiter
How does RWM function?
programmed rod sequence used to limit rod worth such that results of rod drop accident does not exceen 280 CAL/GRM per TS
What enthalpies will cause fuel pellet cracking? Fuel Melting?
170-280Cal/gm cause cracking due to rapid expansion
>280Cal/gm cause fuel pellet melting
Why is RWM not REQUIRED above 10%?
At higher power levels, even with multiple operator errors, a rod drop will not result in enthalpy above 280 Cal/gm
What is required if RWM INOP during Startup?
Suspend rod movement except via SCRAM (IMMEDIATELY)
OR
Verify >12 rods withdrawn IMMEDIATELY
OR
Verify by admin methods that startup with RWM INOP has not been performed in last 12 months
AND
Verify movement of control rods is in compliance with analyzed rod position sequence by second license operator or other qualified tech staff
What is a Withdraw Block?
When a rod is withdrawn one notch past its withdraw limit, withdraw blocks issued to all rods and insert blocks issued to all rods excep the rod with withdraw error
WHat is an INSERT Block?
When rod is inserted one notch past insert limit, then withdraw blocks are issued to all rods except the rod with the insert error and an insert block applied to all control rods except in-step rods
What is the Low Power Setpoint (LPSP)?
Power level at which RWM can be bypassed.
Signals from FWLC determine when you are above LPSP (10%).
WHen FWLC says >10% FW and 10% steam flow for 1 minute, RWM can be deactivated.
What are the RWM Mode Switch Positions?
3 positions - Normal/ Bypass (Bypass only with SRO approval)
Bypass mode used when using “Emergency In” so to prevent rod blocks from keep coming in
What are the RWM Color Schemes?
Rods in latched step are GREEN
Rods in substitute position are YELLOW (Max 10)
Rods OOS are CYAN (Max 8)
Rods w/ insert Error are Magenta (will receive on rod drift in)
Rods w/ withdraw error - Red
Rods w/ unknown - Show ?? in Red
Selected rods show inverse video
What are the CRAM Array?
Control rods pre-selected for insertion quickly to reduce power in emergency - normally 24-48 position
What are the RWM Secondary Functions?
SUBSTITUTE position: only accepted by RWM when rod has bad input from RPIS - MAx 10 - YELLOW
Alternate limits - allow operator to declare a rod to be at the step limit even though it is inserted an even notch further- MAX 2 of 02 or 46 instead of 00 or 48 when below LPSP
OOS - allows control rod to be inserted to 00 regardless of sequence limits
